Wyniki wyszukiwania - BazTech

1

Tribological and material utility aspects of mill rolls for cold rolling

Krawczyk J., Kokosza A., Pacyna J., Madej M.

Inżynieria Materiałowa

|

2017

|

Vol. 38, nr 1

20--25

EN

In the present work, quantitative and qualitative indicators related to wear have been proposed based on the results of the research conducted on damaged mill rolls working in a modernized rolling mill, as well as the technical data related to rolling. It has been found that previously used mill rolls were worn by two main mechanisms, i.e. abrasive wear and fatigue wear. The fatigue mechanism is the main reason for the rolls being removed from further exploitation. Tribological laboratory tests were performed by means of the T05 tester (a block/ring wear testing system) with the load of 100 and 300 N applied for 2000 s. The 100Cr6 bearing steel with the hardness of 57 HRC was applied as the counter-sample. The X153CrMo12 and 70MnCrMo8-2 steels were used as the research material. The tempering temperature of 100 and 150°C were used for the X153CrMo12 steel and 100°C for 70MnCrMo8-2 steel. It has been shown that the steel characterized in a microstructure composed of primary carbides (X153CrMo12 and previously used material). The role of the primary and secondary carbide precipitations as abrasive particles has been indicated in the work. It has also been proven that increasing the tempering temperature results in an increased wear of the 70MnCrMo8-2 steel. The conducted research allows for a proper selection of the tempering temperature (100°C). This confirms the assumed concept of the proposed roll heat treatment. A verification (monitoring) of the working rolls’ wear was based on the observations of the cracks formed during their usage and the roughness measurements carried out at three locations across the width of the strip.

PL

Celem pracy była analiza zależności pomiędzy mechanizmami zużycia walców hutniczych wykonanych z dwóch gatunków stali X153CrMo12 i 70MnCrMo8-2. Analiza odnosi się do prób eksploatacyjnych walców i badań laboratoryjnych materiałów stosowanych na te walce. W walcowni zimnej stosowano walce ze stali X153Cr- Mo12 wykonane według klasycznej technologii obróbki cieplnej. Zwłaszcza w klatce wstępnej, gdzie następuje redukcja z przekroju kołowego na prostokątny, występowały bardzo częste uszkodzenia walców. Walce nie były monitorowane dla ustalenia efektywnego czasu ich pracy przed uszkodzeniem zmęczeniowym. Charakteryzowały się dużą odpornością na zużycie ścierne. Natomiast pasmowe wydzielenia węglików pierwotnych oraz siatka węglików drugorzędowych ułatwiała rozwój pęknięcia zmęczeniowego.

2

The importance of primary carbides for the tribological properties of ferrous alloys

Krawczyk J., Frocisz Ł., Kokosza A., Rożniata E., Dziurka R., Madej M.

Tribologia

|

2016

|

nr 6

69--81

EN

Among the materials used for the mill rolls, one of the main groups are materials with eutectoid primary carbides in their microstructure. The volume fraction and morphology of these carbides influent in a significant way on the tribological properties of tool materials. In the paper, the role of the primary carbides morphology on the fatigue wear of mill rolls after exploitation was presented. The role of the primary carbides morphology in the sliding wear of tool materials was also investigated. The evaluation of the sliding wear mechanism and its degree was performed by the investigation of the mill rolls surface roughness after exploitation. Whereas, the role of ledeburite cementite morphology in wear mechanism changes ware investigated by the laboratory tests. Tests were performed with the use of different loads, time, and temperature during the trials. The microcutting of counter sample material by the primary carbides from the tested samples was observed.

PL

Wśród materiałów stosowanych na walce hutnicze są takie, które w swojej mikrostrukturze zawierają również węgliki powstające w wyniku przemiany eutektycznej. Ponieważ powstają one z cieczy, nazywane są węglikami pierwszorzędowymi. Ilość oraz kształt tych węglików może istotnie wpływać na własności tribologiczne takich narzędzi. W pracy przedstawiono rolę morfologii węglików pierwotnych w zużyciu zmęczeniowym na przykładach walców hutniczych po eksploatacji. Przedstawiono również rolę węglików pierwotnych w zużyciu ściernym. Ocenę zużycia ściernego wykonano na podstawie wpływu czasu eksploatacji na chropowatość powierzchni walców pracujących w walcowni zimnej płaskowników. Natomiast rolę morfologii cementytu ledeburytycznego w zużyciu ściernym badano w warunkach testów laboratoryjnych przy stosowaniu zmiennych obciążeń pary trącej oraz temperatury pracy. Wykazano mechanizm mikroskrawania przez odsłonięte węgliki pierwszorzędowe (jako „mikroostrza”) materiału przeciwpróbki.

3

Prognozowanie czasów przebudów walców w zespole walcowniczym dla potrzeb operacyjnego planowania produkcji

Kubiński W., Niekurzak M.

Hutnik, Wiadomości Hutnicze

|

2014

|

Vol. 81, nr 6

379--384

PL

W artykule przedstawiono komputerowy model wykorzystujący sztuczną inteligencję do wspomagania operacyjnych decyzji technologicznych i usprawnienia systemu planowania produkcji w walcowni taśm na gorąco. Przy planowaniu produkcji taśm stalowych walcowanych na gorąco istnieje konieczność uwzględnienia wielu ograniczeń technologicznych i organizacyjnych, dlatego opracowanie harmonogramów produkcji jest bardzo złożone. Dla prawidłowej pracy walcowni planowanie terminów przebudów walców jest jednak konieczne, ponieważ stanowi element limitujący w procesie produkcji. Do rozwiązania tego problemu zastosowano metody sztucznej inteligencji: system ekspertowy, wykorzystujący w procesie pozyskiwania wiedzy algorytm ID3 oraz klasyczne metody statystyczne regresji liniowej i nieliniowej. Opracowane wyniki badań świadczą o poprawności zbudowanych modeli jako narzędzi wspomagających procesy decyzyjne na szczeblu zarządzania przedsiębiorstwem hutniczym, zarówno na etapie projektowania, jak i eksploatacji istniejących już systemów.

EN

The article presents a computer model based on artificial intelligence methods for operational decision support technology and improve production planning system in hot strip mills. When planning the production of steel strip hot - rolled there is a need to take into account a number of technological and organizational constraints, because the development of production schedules is very complex. But especially crucial to the proper operation of the mill is the appropriate planning conditions reconstructions rolls, because this factor is the limiting element in the production process. To solve the problem the methods of artificial intelligence: an expert system that uses a process of knowledge acquisition algorithm ID3 and classical statistical methods of linear regression and nonlinear. Our results demonstrate the correctness of the proposed models as tools to support decision-making processes at the level of the enterprise metallurgical both the design and operation of existing systems.

4

Nowe materiały i nowe technologie obróbki cieplnej dla hutnictwa w ofercie AGH

Pacyna J., Krawczyk J., Bała P., Kokosza A., Dąbrowski R., Rożniata E.

Hutnik, Wiadomości Hutnicze

|

2010

|

Vol. 77, nr 4

160-166

PL

W pracy opisano nowe materiały i nowe technologie znajdujące się w ofercie Wydziału Inżynierii Metali i Informatyki Przemysłowej AGH dla hutnictwa polskiego i światowego. Zamieszczone oferty podzielono na dwie grupy. Pierwsza grupa to oferty ostatnio wdrożone. Druga natomiast to oferty, nad którymi nadal trwają prace w AGH, lecz ich rezultaty w postaci nowych materiałów i nowych technologii wkrótce zostaną przedłożone wybranym firmom do wykorzystania.

EN

This paper content an offer of the new materials and new technologies of heat treatment for Polish metallurgical industry. The offer was divided on the two groups. First one – a new materials and new technologies, which were recently implemented. The second group content a new materials and new technologies, on which we are still working, however in near future they will be submit for metallurgical companies to use it in practice.

5

Influence of the microstructure and loads on tribological properties of G155CrNiMo4-3-3 cast steel

Krawczyk J.

Archives of Foundry Engineering

|

2010

|

Vol. 10, iss. 3

39--44

EN

Materials for mill rolls, fulfilling high requirements due to difficult exploitation conditions, are cast steels of adamite grade. Those are cast steels of pearlitic matrix with uniformly distributed cementite precipitations (e.g. hypereutectoid). In respect of a microstructure and a chemical composition these steels are hypereutectoid steels. They contain chromium (app. 1 %) and nickel (app. 0.5 %) and sometimes have an increased content of silica. Admissible is also a content of Mo (app. 0.4 %). An uniformly distributed carbide phase can be obtained by the proper heat treatment. The determination of the heat treatment influence on tribological properties - in dependence of the applied load - of adamite hypereutectoid G155CrNiMo4-3-3 cast steel, used for mill rolls - was the aim of the hereby paper. The purpose of the applied heat treatment was to change the hypereutectoid cementite morphology. Tribological tests were carried out at a room temperature by means of the T-05 tester, at loads of: 50, 100 and 150 N. Bearing steel 100Cr6 of a hardness 57 HRC was used as a counter sample. Testing time was 400 seconds. During the test the abrasion products were being removed from the counter sample. The performed investigations allow to draw conclusions regarding the influence of the hypereutectoid cementite morphology and loads on a wear mechanism and intensity of wearing of hypereutectoid adamite cast steel.

6

Influence of a matrix on properties of mottled cast iron applied for mill rolls

Krawczyk J., Pacyna J.

Archives of Foundry Engineering

|

2010

|

Vol. 10, iss. 3

45--50

EN

Mill rolls are ones of the most expensive tools applied in plastic working processes and have to satisfy several criteria, which allow them to be used. Cast iron mill rolls, due to their fracture toughness and tribological properties, are the most often applied at hot-rolling in the last rolling stands. This results from the smallest dynamic loads of such rolling stands and the decisive influence of the surface quality of these tools on the surface quality of the rolled product. An improper microstructure of rolls can lead to their premature wearing, e.g. broken flanges, pivots twisting off etc. By means of the heat treatment the matrix microstructure and morphology of carbide precipitations can be modified and this in-turn can influence cast iron properties. Determination of the influence of microstructure changes, caused by the heat treatment, on the properties of EN-GJN-HV300 low-alloy cast iron, after its modification and spheroidization – is the aim of the present paper. Those changes are based on the formation pearlitic or bainitic matrices at the similar morphology of graphite and ledeburitic cementite precipitations. The performed investigations should enable designing the heat treatment of cast iron metallurgical rolls in such a way as to obtain the optimal microstructures for functional parameters of these type of tools. The influence of changing the pearlitic matrix into the bainitic one on such properties as: hardness, impact strength, tensile strength, creep limit, bending strength and a stress intensity factor KIc was investigated in this study. Samples for testing, the listed above mechanical properties, were taken from an industrial casting with care to have pieces of very similar crystallization conditions.

7

Characteristic of intermetallic phases in cast dental CoCrMo alloy

Podrez-Radziszewska M, Haimann K., Dudziński W, Morawska-Sołtysik M.

Archives of Foundry Engineering

|

2010

|

Vol. 10, iss. 3

51--56

EN

Apart from chromium and molybdenum, casting alloys of cobalt usually contain also up to 0.35 % of carbon. With significant content of carbon, presence of carbide-forming alloying elements results in creating carbide phases. These alloys are characterised by dendritic structure of solid solution of chromium and molybdenum in cobalt with interdendritically precipitated carbides. Because of high chromium content, dominating are M23C6-type carbides, but chromium-rich carbides can be also of M7C3 and M3C2-types. The other elements in the alloy result in creating M6C and MC-type carbides. In the case of low carbon content, creating carbides and forming intermetallic phases based on the alloying elements and cobalt become limited. The presented research was aimed at characterising structure of the cobalt-based dental alloy containing trace quantity of carbon. Characterised were intermetallic phases hardening the alloy. Microscopic examinations using light microscopy, SEM and TEM were carried out. Chemical microanalysis of the precipitates using X-ray analyser EDS was performed, as well as phase analysis using selected area electron diffraction.

8

Zjawiska tribologiczne zachodzące na powierzchni czopów żeliwnych walców hutniczych

Krawczyk J.

Tribologia

|

2008

|

nr 3

17-26

PL

Celem niniejszej pracy było określenie roli mikrostruktury w zużyciu tribologicznym czopów trzech żeliwnych walców hutniczych. Specyfika układu trącego, występującego pomiędzy czopem walca i łożyskiem, może sprzyjać zwłaszcza zużyciu przez pitting, spalling i fretting. Mogą one wpływać na parametry łożyskowania walca, a nawet stwarzać niebezpieczeństwo uszkodzenia czopa walca. Dlatego gromadzone są dane dotyczące również zjawisk tribologicznych zachodzących na czopach walców hutniczych. W pracy badaniami objęto trzy walce, w których podczas eksploatacji uległy wyłamaniu czopy. Walce te zostały wykonane z żeliw połowicznych (pstrych). Oznacza to, że w mikrostrukturze walców obok płatkowych wydzieleń grafitu występuje również ledeburyt przemieniony. Miały one osnowę martenzytyczno-bainityczną z bainitem dolnym. W osnowie tej można wyróżnić również obszary, które powstały w wyniku przemiany dyfuzyjnej. Są to wydzielenia troostytu, które zarodkują na cementycie ledeburytycznym lub na wydzieleniach grafitu. Stwierdzono, że warunki tribologiczne, występujące na powierzchniach żeliwnych walców hutniczych, sprzyjają zużyciu mechanizmem pittingu. Wykruszone w wyniku oddziaływania tribologicznego fragmenty cementytu ledeburytycznego oddziaływają w węźle tarcia jako ścierniwo. Ponadto duże fragmenty czopa walca mogą ulegać wykruszeniu w wyniku rozwoju pęknięć wzdłuż ciągłej siatki cementytu ledeburytycznego.

EN

This work was focused on determining the role of the microstructure in the tribological wear of the roll necks of three cast iron metallurgical rolls. The specificity of wear between the roll neck and bearing may be conducive to wear by pitting, spalling, and fretting. They may influence the parameters of the bearing system of roll and even cause the failure of the roll neck. Therefore, the author collected the data related to tribological phenomena occurring on the surfaces of the roll necks of metallurgic rolls. In this study, three rolls with broken roll necks were chosen for investigations. These rolls were made of mottled cast iron. It means, that both flaky precipitations of graphite and transformed ledeburite are present in the martensitic-bainitic (with lower bainite) microstructure of these rolls. The areas formed as the result of phase transformation may also be observed in the microstructure of the roll. These areas were identified as precipitations of troostite, which nucleate on ledeburitic cementite or on precipitations of graphite. It was found that tribological conditions being present on the surfaces of cast iron rolls are conducive to the wear by pitting. The fragments of ledeburitic cementite formed by spallation during tribological wear act in the friction area as abradant. Moreover, large fragments of the roll neck may spall off in the consequence of crack propagation along continuous net of ledeburitic cementite.

9

Structural causes of defects in a cast iron mill roll

Krawczyk J.

Archives of Foundry Engineering

|

2008

|

Vol. 8, iss. 2

93-98

EN

This paper describes an analysis of a defective microstructure of a mill roll. For this purpose, a piece of a broken roll was collected. That roll was made of mottled cast iron. Its microstructure consisted of modular graphite, transformed ledeburite and a matrix composed of bainite and martensite. Metallographic investigations were performed nearby the fracture in the roll. Observations were conducted on polished sections, first not etched, and then etched, which allowed us to trace carefully the propagation of the fracture. There was found a strict correlation between the microstructure of the roll and the progress occurring in the crack. It was ascertained that the basic reason for the damage to the roll was banded precipitations of ledeburitic cementite. In addition, cementite formed a continuous network. Another microstructure defects of that roll are also precipitations of secondary carbides on the boundaries of former grain of austenite as well as the occurrence of upper bainite in its matrix. The results obtained hereunder allow broadening the data base relative to the genesis of damages to mill rolls, which in future will permit one to design a proper microstructure of cast iron mill rolls. Proper microstructure of cast iron mill roll should be shaped at the stage of designing the chemical composition, conditions of crystallization or heat treatment if any.

10

Effect of the microstructure on tribological phenomena occurring on the surface of a mill roll made of SA5T cast iron (GJSL-HV600 - GJSL-330NiMoCr12-8-3)

Krawczyk J.

Archives of Foundry Engineering

|

2008

|

Vol. 8, iss. 2

170-174

EN

This paper deals with the role of the microstructure in the tribological wear processes occurring in a cast iron mill roll. For this purpose, a piece of a broken roll, made in Italy, was collected. Its microstructure consisted of modular graphite, transformed ledeburite and a matrix composed of bainite and martensite. Metallographic investigations were performed on the roll working surface in conjunction with metallographic tests effected within its surface layer. There was established the relation between the microstructure of the roll and the process of its tribological wear. The following was ascertained: micro-shrinkages or graphite precipitations nearby the working area cause cracks between those places and the working area; in the surface layer, cracks occur usually in the zone of ledeburitic cementite. At places of considerable precipitations of ledeburitic cementite, the tribological wear intensity of the roll is lower. A banded layout of precipitations of ledeburitic cementite facilitates a selective spalling of some parts of the roll material. The results of this study allow broadening the data base related to the effect of the microstructure on tribological wear of mill rolls, which in future will permit one to design their proper microstructure of cast iron mill rolls.

11

The role of metallurgical defects and microstructure on failure formation in roll necks of cast iron rolls

Krawczyk J., Pacyna J.

Metallurgy and Foundry Engineering

|

2007

|

Vol. 33, no. 2

89-96

EN

This work presents the examples of structural reasons for failure of the necks of cast iron rolls. The most common reason for damage of metallurgical roll necks is a presence of shrinkage porosity in their volume. Moreover, a high fraction of ledeburitic cementite can lead to the formation of a continuous net of eutectic carbides, which facilitate cracking. Even very thin net of secondary carbides, formed on the boundaries of former grain of austenite, can significantly facilitate propagation of the crack. Continuous net of ledeburitic cementite, in the case of its precipitation in a form of bands and existence of hardened areas in the alloy matrix can lead to roll neck fracture relatively easy. The use of flake graphite cast iron for metallurgical rolls increases a risk of the fracture of roll neck.

PL

W niniejszej pracy przedstawiono przykłady strukturalnych przyczyn uszkodzeń czopów w żeliwnych walcach hutniczych. Najczęstszą przyczyną uszkodzeń czopów walców hutniczych jest zaleganie w nich obszarów rzadzizn. Ponadto duży udział cementytu ledeburytycznego może prowadzić do powstania ciągłej siatki węglików eutektycznych, która tworzy drogę łatwego pękania. Nawet bardzo cienka siatka węglików drugorzędowych utworzona na granicach pierwotnego ziarna austenitu może w znaczący sposób ułatwiać rozwój pęknięcia. Ciągła siatka cementytu ledeburytycznego, w przypadku jego wydzielania w postaci pasmowej oraz występowanie w osnowie obszarów podhartowanych, może doprowadzić do łatwego złamania czopa walca. Zastosowanie na walce hutnicze żeliwa z grafitem płatkowym zwiększa niebezpieczeństwo złamania czopa.

12

Effect of tool microstructure on the white layer formation

Krawczyk J., Pacyna J.

Journal of Achievements in Materials and Manufacturing Engineering

|

2006

|

Vol. 17, nr 1-2

93--96

EN

Purpose: Purpose of this paper: This work supplements the knowledge concerning formation of the white layer on the surface of the tools being utilized in high temperature metal forming processes. Eight iron-based materials were tested: 3 ledeburitic cast steels, 2 hypereutectoid cast steels, normalized and stress relief annealed steel, hardened and tempered steel and nodular mottled cast iron. Design/methodology/approach: The exploitation tests were performed on the hot rolling mills for selected rolled sections, rolling stands and roll passes. The samples were cut out of the roll in such a way that they contained the roll working surface and were used for metallographic observations of the subsurface zone. Findings: It was found, that uniform distribution of dispersed precipitates of hypereutectoid cementite in the alloy matrix prevents the formation of the white layer on the surface of the rolls. Research limitations/implications: The white layer definition was given. An influence of the microstructure of iron base alloys on the susceptibility to form the white layer on their surface due to tribological contact was also determined. Practical implications: The procedure for obtaining rolled products of better quality as well as for restricting the probability of roll cracking was proposed. Obtained results should allow proper design of the microstructure of the materials for tools. Originality/value: This work contains several new aspects, which are: the unique tribological conditions for performing the tests, wide range of investigated materials, and combining the microstructure of the material with the susceptibility of the formation of the white layer on its surface. The results of this research may be used by the producers of tools for high temperature metal forming.

13

Warunki powstawania i własności białej warstwy

Pacyna J., Krawczyk J.

Hutnik, Wiadomości Hutnicze

|

2005

|

Vol. 72, nr 11

545-553

PL

W pracy podjęto próbę usystematyzowania informacji dotyczących tzw. białej warstwy. Opisano jej morfologię, mechanizm tworzenia. miejsca występowania, własności oraz skutki powstawania. Ponadto zdefiniowano pojęcia: biała warstwa, ciemna warstwa, warstwa Beilby'ego oraz adiabatyczne pasmo ścinania.

EN

Trials of information systematization relative to so called white layer were undertaken in this work. The morphology, formation mechanism, areas of occurrence, properties and formation effects of the white layer have been described- Moreover, notions of: white layer, dark layer, Beilby layer and adiabatic shearing band have been defined.

14

Analiza stanu naprężenia i odkształcenia walców hutniczych

Gąsiorek D.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2002

|

z. 19

39-44

PL

Walce dla walcowni bruzdowych średnich i drobnych wykonywane są zazwyczaj w postaci walców monolitycznych odlewanych lub kutych, w których po wykorzystaniu warstwy roboczej i osiągnięciu średnicy martwej walca, następuje jego złomowanie. W celu obniżenia kosztów eksploatacji można zastosować walce składane. W pracy przedstawiono modele prototypowych walców składanych dla walcowni średnio-drobnej. Do opisu cech geometrycznych walców wykorzystano program AnSys 5.6, w którym również zostaną przeprowadzone obliczenia numeryczne. W pracy zostaną przedstawione przyjęte do obliczeń modele, wyniki symulacji komputerowych w postaci map naprężeń i przemieszczeń oraz wnioski końcowe.

EN

Rolls for medium sulcal rolling-mill are usually produced in the form of monolithic casted rolls or forge, in which after working layer utilization and achievement of dead diameter of rolls, its dumping follows. To of lower costs of exploitation it is possible to apply folded rolls. The FEM model of composite rolls prototypes for shape mill is presented in the paper. The system has been modeled using AnSys 5.6 software. In this work models, results of computer simulation in form of maps of stress and displacement as well as final conclusions will be introduced.